In the food industry, pieces of food are often packaged together in a single pack. U.S. Pat. No. 6,799,684 discloses a counting and portioning system which counts discrete articles that conform to predetermined specifications into lots having a predetermined number of articles or a target volume. The system includes at least one portioning bin positioned to receive articles from a conveyor. The at least one bin has at least first and second outlet gates for emptying articles into separate respective first and second locations. A scanner detects and maintains a count of articles that are received in the at least one portioning bin and fall within the predetermined specification. The detector unit generates an out-of-specification signal when an article or group of articles received in the at least one portioning bin falls outside the predetermined specification. A control unit causes the first outlet gate to open when the count or volume of articles is equal to the predetermined number and causes the second outlet gate to open in response to receipt of an out-of-specification signal. The profile/volume signature for every part scanned and delivered from the infeed to the scanner is stored.
However, some situations in the food industry are such that U.S. Pat. No. 6,799,684 is inadequate. For example, when pork chops are packaged, the individual pork chops which make up the batch within a pack are often placed by hand on a plastic or polystyrene tray which is then wrapped. This is done manually because pork chops are quite difficult to handle in an automated system, and whilst some processes have been automated, it has previously been found necessary for the individual chops to be processed extensively by hand so as to identify chops which are misshapen or which should be rejected for some other reason. On a production line, it is possible for off-cuts of meat to be present which should not be included in the tray. For example pieces of meat which are at the end of a primal cut of pork loin which is cut up might need to be removed from the production line without being packed. A primal cut is a larger section of an animal carcass which is cut up to form cuts which are sold in shops. For example, a pork loin is cut up to form a number of cuts which are sold in shops including chops, cutlets and loin. Additionally, the meat packaging industry has had difficulty in putting individual pieces of meat together to form a batch on a tray in such a way that the pieces of meat are placed in the tray accurately and with some regard to the presentation of the pieces of meat within the pack. FIGS. 1 and 2 show a pack of meat in which four chops 1 are positioned within a tray 2. The chops 1 are positioned within the tray so as to overlap each other which not only reduces the size of the tray required to form the pack, but is also pleasing to the eye of the buyer of the pack 3. The buyer is able to see each of the chops 1 which is in the pack 3. This is reassuring because the end buyer is able to judge the freshness of the visible chops 1. The tray would normally be closed by a plastic film later in the production process, although the film is not shown in FIGS. 1 and 2.
As mentioned above, the chops 1 are often placed in the tray 2 by hand in order to ensure their correct arrangement within the tray, and to remove any off-cuts or other pieces of meat which are not appropriate to include in the pack 3.
Some automated machinery has been proposed. For example, it has been proposed to use a retractable conveyor in order to load items on to a tray. An example of such a machine would be the QuickLoader made by Marel hf. The QuickLoader is a servo-controlled retractable conveyor which loads items into trays or onto another conveyor, and is able to position the item in the tray or on the other conveyor accurately. The retractable conveyor includes a region of conveyor which, on retraction, is quickly removed from beneath the item which it is transporting. This allows the item to drop, and because the item is positioned substantially above the position it is intended to put the item, it drops into the correct position. However, it is only known to use such a machine so as to drop items into a tray one at a time, and by dropping them into the tray from slightly different positions, the overlapping arrangement shown in FIGS. 1 and 2 can be achieved. There are various ways of removing off-cuts. If an off-cut item travels along the conveyor, a mechanical arm could extend across the belt to remove it from the conveyor, or a robot arm using machine vision could identify and pick up off-cut items, or the off-cut is simply run off the end of the retractable conveyor to a suitable area for disposal. If, for example, the conveyor is programmed to place four pieces of meat in the tray, these are added one at a time, and each piece of meat is dropped into the tray from a slightly different position in order to achieve the overlap. However, because each piece of meat is added individually, it is felt that the machine can be made quicker by supplying a number of items to the conveyor which have already been formed into the batch which is to be dropped into the tray. Unfortunately, this leads to a number of difficulties which the inventors of the present application have sought to solve. It is not always possible to supply all of the items required to fill a batch in one go, and so the batch of items supplied does not always form a complete batch. This might be because of the presence of an off-cut, or for example a quality control system which rejects an item based on some predefined criteria. In this case, the incomplete batch may have to be rejected in order to free the production line for the next complete batch. Clearly, this is wasteful. The present invention aims to reduce the wastage and improve operation.